PROJECT SUMMARY The commuting environment is recognized to present a major risk to worker safety. Recent work shows that daily work conditions and work-related strain reactions influence unsafe commuting behaviors, but the mechanisms driving these relationships remain poorly understood. The major impediment to this search for mechanisms has been an inability to objectively model what is happening with the driver and on the road immediately prior to and during unsafe commuting events. The proposed project brings together an inter-disciplinary team of experts from the occupational safety and health, transportation safety, and psychological communities to overcome this impediment. The project team will integrate an existing daily survey approach to work stress with a video-based, naturalistic driving approach validated in the transportation safety community to explicate the process through which daily work conditions and work-related strain reactions influence unsafe commuting. This approach will be applied in a longitudinal study of 100 full-time employees who will complete twice daily surveys and have their driving and in-vehicle behaviors observationally tracked across eight consecutive weeks of daily commuting. The project team will demonstrate that (1) daily work conditions and work-related strain reactions influence same- day post-work unsafe commuting via attention and distraction mechanisms and that (2) daily work conditions and work-related strain reactions influence next-day pre-work unsafe commuting via a fatigue mechanism. The project team will also evaluate whether the influence of daily work conditions and work-related strain reactions on unsafe commuting via these within-commute mechanisms strengthens over the course of the work week. The proposed project is directly responsive to the NIOSH Traumatic Injury Prevention Cross-Sector, which is devoted to the prevention of injury and death stemming from sudden events such as motor vehicle crashes. As commuting is a ubiquitous activity in worker?s daily lives within many industries and occupations, the proposed project will have direct applications to worker safety in almost all occupational groups. The proposed research is expected to have major implications for intervention targeting and development, which will yield a strong contribution to NIOSH?s Research to Practice (r2p) initiative. The proposed project will provide outputs of cross-disciplinary publications and presentations in the occupational safety, applied psychology, and transportation safety communities that will contribute to the intermediate outcome of guiding intervention development to lay the groundwork to achieve the long-term outcome of reducing rates of worker injury and death while commuting.